The world is currently experiencing revolutionary changes in communications systems, brought about by the general availability of access to the Internet as well as the evolution of wireless telephony and Intelligent Network (IN) service enhancements to the Public Switched Telephone Network (PSTN). In particular, interest in Internet Protocol (IP) telephony, or Voice over IP (VoIP), has expanded rapidly as the associated technologies have matured. Improved interoperability is a critical factor to further enhancements in such communications systems, particularly telephony services provided by such systems.
The advent of IP telephony allowing phone calls across packet-switched networks triggered a revolution in the telecommunications industry. Early IP telephony, however, had many limitations that prevented it from becoming a mainstream telephony service. One of the biggest problems was a lack of connectivity between an IP telephony network and the public switched telephone network (PSTN). This led to the development of a gateway that allows IP and PSTN customers to communicate with each other. Differences in the protocols used by the Internet and PSTN, however, have required the development of novel solutions to resolve problems of interoperability between the networks.
Associated with the North American PSTN is a signaling network that employs the Common Channel Signaling System 7 (SS7) to exchange signaling messages between network elements, or "nodes." Every network must have an addressing scheme, and the SS7 network is no different. Network addresses are required so that a node can exchange signaling messages with nodes to which it does not have a physical signaling link. In SS7, addresses are assigned using a three-level hierarchy. Individual signaling points are identified as belonging to a "cluster" of signaling points. With each cluster, each signaling point is assigned a "member" number. Similarly, a cluster is defined as being part of a "network." Any node in the American SS7 signaling network can be addressed by a three-level number, or "point code," defined by its network, cluster and member numbers; each of these numbers is an 8-bit number and can assume values from 0 to 255. A signaling message is transmitted from an originating signaling point, identified by an "origination if point code" (OPC), to a destination signaling point, identified by a "destination point code" (DPC).
Packet-switched networks which use the Internet Protocol (IP), such as the Internet, use an address format that is unlike the three-level point codes used in the North American SS7 signaling network. According to the Internet Protocol Version 4 (IPv4), the addresses of network nodes are always 32 bits in length, and are typically written as a sequence of four numbers representing the decimal value of each of the address bytes. Because of differences in the addressing protocols employed in the PSTN signaling network (e.g. SS7) and other packet-switched networks, such as the Internet, interoperability between the networks can be limited. With the proliferation of IP telephony devices and other Internet applications, however, it is desirable to provide access to certain resources generally only available through the PSTN signaling network. For example, an Internet telephony device could benefit from access to "800" number databases, Service Data Points (SDPs) and Home Location Registers (HLRs) coupled to the PSTN signaling network, as well as Intelligent Network (IN) services available through the PSTN signaling network. Furthermore, the PSTN signaling network might be used when alternate routing of messages is needed, such as in the case of Local Area Network (LAN) or Wide Area Network (WAN) crashes. Because of the proliferation of IP telephony devices and services, and the desire to provide Intelligent Network (IN) services to telephony devices coupled to packet-switched networks, such as the Internet, there is a need in the art for systems and methods for routing a message from a packet-switched network through a signaling network associated with a Public Switched Telephone Network (PSTN).